One quarter of persons with adenocarcinoma of the lung develop brain metastases. The central nervous system is also emerging as a major site of first relapse after initial success with drugs targeting EGFR. Despite treatment, two thirds of patients with cerebral metastases experience neurological symptoms and many succumb to this manifestation of lung cancer. Animal model systems of brain metastasis are few. As a result, little is known about the genes and functions that enable lung adenocarcinomacells to colonize the brain. We have combined the power of unbiased DNA array-based profiling of gene expression with in vivo functional selection of organ-specific metastatic cells to identify genes that mediate organ-specific metastasis. We previously validated this experimental strategy in studies on breast cancer metastasis to bone and lung. Our results to date show that tumor cells utilize different sets of genes to colonize different organs. We are applying this approach to the problem of brain metastasis by lung adenocarcinoma cells. By means of in vivo selection of brain metastatic subpopulations from H2030 lung adenocarcinoma cells, and comparative transcriptomic analysis, we have identified a lung-to-brain metastasis signature consisting of genes whose expression is linked to brain metastatic behavior. Building on this preliminary work, we will expand the identification of brain-specific lung cancer metastasis genes to other KRAS mutant and EGFR mutant cell lines, and to malignant cells from pleural effusions and mediastinal lymph nodes from MSKCC patients. We will functionally validate brain-specific metastasis genes in brain metastasis assays in mice. In collaboration with Marc Ladanyi (Core A), we will determine the association of the experimental lung-to-brain metastasis signature with the clinical outcome of brain metastasis. We will determine which of the lung-to- brain metastasis signature genes mediate disruption of the blood brain barrier and invasion of the brain parenchyma. Based on these cell lines and genes we will develop preclinical models for testing the effectiveness of, and resistance to, the therapeutic agents studied by Harold Varmus (RP4), William Pao (RP3), and Neal Rosen (RP2). Thus, we will combine unique experimental approaches, novel technologies and complementary collaborations within this Program Project to identify the determinants of lung adenocarcinoma brain metastasis and its susceptibility to therapeutic intervention.